1. Field of the Invention
This invention relates to communication systems and methods for transferring multimedia and packet data, in either direction, between a host system and a station in a FDDI or token passing network and managing bandwidth at a station in real time. More particularly, the invention relates to communication systems and methods for real time, dynamic management of bandwidth on a station in a FDDI or token passing network transferring data, in either direction, between the network and a host system.
2. Description of the Prior Art
Prior art systems for communicating in either direction multimedia and packet data between a host system and a FDDI and managing bandwidth include the following:
U.S. Pat. No. 4,862,451 describes switching apparatus and a method for transferring information between channels carrying synchronous information traffic and channels carrying asynchronous data packet traffic. The apparatus interrupts asynchronous packet transmission at the end of a preselected time frame and re-arranges finished or established connections in accordance with a flexible arbitration scheme to support synchronous and asynchronous traffic in a single exchange operation.
U.S. Pat. No. 5,043,981 describes a data flow controller which detects various conditions of a particular queue of an output buffer memory receiving framed data of a particular priority when the amount of storage remaining available for the particular queue is not greater than the predetermined storage capacity of the memory. In response to selected conditions, the controller terminates transfer of data from the system memory to the controller memory and initiates transfer of data, having a different priority from the system memory through the controller memory to a particular queue of the output buffer.
U.S. Pat. No. 5,245,605 describes a method and apparatus for controlling the transmission of a first class of traffic which is transmitted on a ring network with a second class of traffic. The '605 Patent provides for the transmission of a first control signal where both classes of traffic may be transmitted on the ring if current protocols permit. The first control signal will be changed to a second control signal if, after the first control signal is transmitted at least once around the network, the first control signal reaches a station having a backlog of second class traffic. The second control signal is transmitted once around the network to indicate to each station that it may not transit the first class traffic. The first class of traffic is usually asynchronous data while the second class of traffic is usually synchronous data.
U.S. Pat. No. 5,392,280 describes a data transmission system and scheduling protocol utilizing both synchronous transmission and asynchronous transmission in an alternating pattern to provide each user with a guaranteed transmission bandwidth or capacity to accommodate real time communication. The synchronous time slots provide for the bandwidth guarantees while the asynchronous time slots are used to transmit data when a part of a previous synchronous slot is not used. The asynchronous time slots also permit asynchronous data transmission using unallocated time within a given time frame.
U.S. Pat. No. 5,208,809 describes a node for use with asynchronous and synchronous communication networks to indicate interconnect data systems with networks having transmission paths interconnecting network nodes. Clock apparatus synchronizes a flow of data on an incoming transmission both within the node at a pulse rate of the generated clock pulses independent of a data transfer rate on the data flow on both the incoming and outgoing transmission paths.
U.S. Pat. No. 4,665,518 describes a data bus system including a plurality of serially connected active terminals configured to receive data and either, retransmit the received data or transmit new data to the next adjacent terminals. The system is devised where a plurality of user data sinks may receive synchronous data occurring at predetermined times and asynchronous data occurring at random times.
U.S. Pat. No. 5,206,857 describes a technique for distributing timing synchronization among selected nodes of a ring network. Clock synchronization is optionally and independently available to a node in the system which simultaneously supports both synchronous and asynchronous data transfer. Each node includes a clock for supplying timing information to equipment at the node. A master node measures time delay encountered by data in the network and transmits the measurement to a slave node. The difference between the master and slave measurement adjusts the clock at the slave node.
U.S. Pat. No. 4,763,321 describes a system for dynamically allocating circuit slots in frames which are used for exchanging bits between users connected to nodes of a communication network linked by means of medium links having transmit and receive interfaces. The frames are delimited by flags and divided into bit slots which may be used for synchronous circuit flow or asynchronous packet flow. The system insures a dynamic allocation of bandwidths to circuit or packet switched bit users according to user activity.
None of the prior art discloses apparatus and method in a communication network for switching between synchronous and asynchronous data and dynamically guaranteeing bandwidth for the traffic in either direction between a host bus system and a FDDI system. The method and apparatus further provide for (1) giving multimedia traffic preference over packet traffic; (2) managing the data flow within the bandwidth of the network; and (3) early capture of a token before multimedia or packet data has been buffered for transmission.